Bad state: Future already completed

[bsutton]

dart --version
Dart SDK version: 2.12.0-259.12.beta (beta) (Fri Feb 12 11:00:34 2021 +0100) on "linux_x64"

I should note that I'm using the project https://pub.dev/packages/dswitch to switch between beta/stable version of dart.

I've seen the below error a couple of times now but haven't been paying much attention ( think it may have happened during unit testing?)

dart pub upgrade --null-safety
Because every version of node_mgmt_lib from path depends on path 1.7.0 and nj_build_all depends on path >=1.8.0-nullsafety.3, node_mgmt_lib from path is forbidden.
So, because nj_build_all depends on node_mgmt_lib from path, version solving failed.
Unhandled exception:
Bad state: Future already completed
#0      _AsyncCompleter.complete (dart:async/future_impl.dart:45:31)
#1      _NativeSocket.tryConnectToResolvedAddresses.connectNext.<anonymous closure> (dart:io-patch/socket_patch.dart:847:16)
#2      _NativeSocket.issueWriteEvent.issue (dart:io-patch/socket_patch.dart:1214:14)
#3      _NativeSocket.issueWriteEvent (dart:io-patch/socket_patch.dart:1221:12)
#4      _NativeSocket.multiplex (dart:io-patch/socket_patch.dart:1242:11)
#5      _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:184:12).
Attempt:11 waiting for isolate vm-isolate to check in
Attempt:11 waiting for isolate dartdev to check in
Attempt:12 waiting for isolate vm-isolate to check in
Attempt:12 waiting for isolate dartdev to check in
Attempt:13 waiting for isolate vm-isolate to check in
Attempt:13 waiting for isolate dartdev to check in
Attempt:14 waiting for isolate vm-isolate to check in
Attempt:14 waiting for isolate dartdev to check in
Attempt:15 waiting for isolate vm-isolate to check in
Attempt:15 waiting for isolate dartdev to check in
Attempt:16 waiting for isolate vm-isolate to check in
Attempt:16 waiting for isolate dartdev to check in
Attempt:17 waiting for isolate vm-isolate to check in
Attempt:17 waiting for isolate dartdev to check in
Attempt:18 waiting for isolate vm-isolate to check in
Attempt:18 waiting for isolate dartdev to check in

The problem doesn't occur if I just run dart pub upgrade

[mkustermann]

/cc @mraleph @a-siva Do we have someone to look at dart:io bugs?

[mraleph]

This might be related to DNS resolution changes

/cc @aam

[aam]

DNS resolution change(looking up ipv4 and ipv6 in parallel) targeted osx, should not have affected other os.

@bsutton how easy is to reproduce the failure? Are you issuing dart pub upgrade --null-safety from the shell or it is executed by dswitch? Has it started from a particular revision (of dart or flutter)?

[bsutton]

Dswitch just creates a sym link to the SDK and the link is on the path so dswitch plays no part in running dart. For this project it occurs every time.

…

On Sat, 20 Feb 2021, 3:01 am Alexander Aprelev, ***@***.***> wrote: DNS resolution change(looking up ipv4 and ipv6 in parallel) targeted osx, should not have affected other os. @bsutton <https://github.com/bsutton> how easy is to reproduce the failure? Are you issuing dart pub upgrade --null-safety from the shell or it is executed by dswitch? Has it started from a particular revision (of dart or flutter)? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#45047 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAG32OGG3KEQUS3PSK6FXYTS72DOJANCNFSM4X3KWNRA> .

[bsutton]

This is a dart project not flutter and in using the stand-alone dart sdk

…

On Sat, 20 Feb 2021, 3:01 am Alexander Aprelev, ***@***.***> wrote: DNS resolution change(looking up ipv4 and ipv6 in parallel) targeted osx, should not have affected other os. @bsutton <https://github.com/bsutton> how easy is to reproduce the failure? Are you issuing dart pub upgrade --null-safety from the shell or it is executed by dswitch? Has it started from a particular revision (of dart or flutter)? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#45047 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAG32OGG3KEQUS3PSK6FXYTS72DOJANCNFSM4X3KWNRA> .

[mraleph]

DNS resolution change(looking up ipv4 and ipv6 in parallel) targeted osx, should not have affected other os.

We did go from Future<List<int>> to Stream<List<int>> on other OSes which might have changed something in ordering of async events in the event queue. I would not be surprised if the bug was already present before we touched the code (the whole function was always painful to look at - so convoluted it was).

I'd suspect cancellation as the source of this issue due to suspicious non-symmetry in the code: notice how many places where result.complete is called we check if result.isCompleted first, one of them has the following comment // Might be already completed via onCancel.

Indeed the following test case seems to reproduce the problem, or at least something that looks like the same exception:

$ cat /tmp/repro.dart 
import 'dart:io';

void main() async {
  try {
    final task = await Socket.startConnect('google.com', 80);
    task.cancel();
    await task.socket;
  } catch (e) {}
}
$ dart /tmp/repro.dart
Unhandled exception:
Bad state: Future already completed
#0      _AsyncCompleter.complete (dart:async/future_impl.dart:45:31)
#1      _NativeSocket.tryConnectToResolvedAddresses.connectNext.<anonymous closure> (dart:io-patch/socket_patch.dart:847:16)
#2      _NativeSocket.issueWriteEvent.issue (dart:io-patch/socket_patch.dart:1214:14)
#3      _NativeSocket.issueWriteEvent (dart:io-patch/socket_patch.dart:1221:12)
#4      _NativeSocket.multiplex (dart:io-patch/socket_patch.dart:1242:11)
#5      _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:184:12)

[aam]

Thanks @mraleph . That was a good idea for a test. Have https://dart-review.googlesource.com/c/sdk/+/186641 for that.
Hopefully this fixes what @bsutton hit.

[eernstg]

Warning, completely off topic Am I the only one who thinks the title 'Bad state: Future already completed' is funny? 😄

[aam]

@bsutton if you have a chance could you please give a try to dart sdk with the fix from the above to see if it improved things for you? 2.13.0-71.0.dev is the first dev build that has the fix in it. That dev version has not been made available on https://dart.dev/tools/sdk/archive yet, so until it is published, you can try main channel (https://dart.dev/tools/sdk/archive#main-channel-url-scheme)

[aam]

https://dart.dev/tools/sdk/archive has 2.13.0-93.0.dev available that should have anticipated fix.

[mraleph]

@aam @a-siva I think we should file CP for stable for this issue if we have not already